AstroHub: An Imaging Management Project

This project has been updated to the AstroHub 2.0, you can see the new article here.

INTRODUCTION

An imaging session involves a lot of preliminar tasks to be done before start imaging. Once the mount, telescopes, and cameras are assembled, one has to connect the equipment to a computer in order to operate it and allow a data flow. The equipment has to be powered also, so additional connections are needed. To manage all this cables isn’t easy: the mount has to be able to move to any coordinates of the sky and there is a real danger to snag the cables if they are not routed correctly.

In addition, once the equipment is ready and one starts imaging, there are many accesories that are necessary: bathinov masks to help focus, flat panels to perform flat flames, a head lamp…

A good management of all the stuff that involves an imaging session sets the difference between a pleasant imaging session and a tedious an unsuccessful one. I had too much unsuccesful imaging sessions in the past, most of them trying to fix unexpected issues with connections, power failures, going inside home to take forgotten accesories… It started to be boring, so I thought on how I could improve this. Commercial solutions are expensive (like all in astrophotography!) and didn’t fit my needs at 100% so I started my own AstroHub project.

After a few months of calculations, prototypes and tests, this is the result: A portable suitcase that allows me to fully manage an astrophotography session in a very short time.

IMG_20180721_172704

It has been optimized to use only 3 cables to connect and power all the equipment quickly and safely. In fact, I spend only 2 minutes to connect all the equipment and once the imaging session has started I can go to sleep without fear of any cable being hooked, even when pier flips are performed.

IMG_20180715_180102

THE ASTROHUB AT A GLANCE

The Astrohub is divided into separated spaces including:

IMG_20180715_181644
  • Power HUB to power the equipment:
IMG_20180715_181821

The Power Hub has 3 circuits:

  • Data Circuit: That gives up to 12V/6A for the electronic devices that transer data (in my case, 2 cameras and a mount).
  • Motors Circuit: Powered with a 12V/4A power supply for motors and other noisy electronics. To separate data lines from motors lines is important to avoid the introduction of noise in the images.
  • PC Circuit: With a power supply that gives 12-20V/5A for a laptop. It can be powered with 220V AC or 12V DC,

It includes also a Control Panel to manage the circuits. For each circuit there is a switch, a RCA connector used as a DC IN/OUT, a fuse, and a Volt/Amp digital meter. It has also a computer fan to cool the power supplies.

It can be powered with the included AC plug at 220V AC, or connecting 12V batteries to the DC IN/OUT connectors.

  • A Data HUB to control the equipment:
IMG_20180715_181922_HHT

It connects the equipment with the computer through a powered USB 3.0 Hub with 10 data ports and 2 charging ports. The hub is rated as 12V/4A Max, and has led indicators to check the status of the connections. The device has been oriented upwards for better accesibility.

  • A Cable HUB
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Consists in only 2 «master cables» to connect all the setup, one for the astronomical equipment and one for the laptop.

The Equipment Master Cable includes a USB 3.0 interface for an imaging camera, 2 USB 2.0 to connect a guide camera and a mount, operated with EQMOD, and a 12V DC connector to power the TEC of the imaging camera. This master cable has been marked to know were to be clamped to the mount quickly and safely. Data cables are shielded to protect data from electronic interferences.

The PC Master Cable has a USB 3.0 interface coming from the USB Hub and a power connector to power a laptop without the need of an additional power supply.

  • The Accesories are organized in 2 spaces.

There is an organized attached to the lid that I use to store Bathinov masks, caps, a mylar film (to protect the equipment against temperature when let outside)…

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…and a DIY Flat Panel made with a iluminated panel for telescopes up to 8″.

IMG_20180721_162102

Inside the main container of the case there is also a notebook and a bag with additional accesories

IMG_20180721_172911

Inside the bag there is a bluetooth mouse, a led lamp powered by USB, a MicroUSB cable to power the flat panel, a bubble level and some tools

Note: This bag has to be optimized yet.

dav

HOW TO USE THE ASTROHUB

To use this Astrohub is quite simple:

  1. Put the Astrohub on the ground, below the tripod.IMG_20180715_173701.jpg
  2. Get the AC Cable, plug it.IMG_20180715_180024.jpg
  3. Get the Equipment CableIMG_20180715_173805_NOTED.jpg
  4. Use the first mark on the cable to clamp it to the polascope cover holder.IMG_20180715_174308.jpg
  5. Use the second mark on the cable to clamp it to the dovetail knobsIMG_20180715_174636.jpg
  6. Connect the camerasIMG_20180715_174730
  7. Connect the mountIMG_20180715_174845
  8. Power the equipmentIMG_20180715_183710_HDR.jpg
  9. Get the PC Cable and connect it to the LaptopIMG_20180715_175114.jpg

And it’s done, the equipment is prepared to be controled by the corresponding software and start imaging.

If you are interested in how this device has been developed, you can find more information below.


DEVELOPMENT OF AN ASTROHUB

BACKGROUND

As most of the amateur astrophotoraphers I started with something like this:

ViajeGarrotxa08- 494

Tons of cables everywhere. A total nightmare in terms of time to setup and reliability. Long time to setup the equipment every night and a lot of nights wasted with connection problems.

I made a first attempt to an AstroHub by attaching all the devices that I could in a plastic sheet.

DSC01327

That was far better, but not enough. It had no case so in case of multiple days sessions I had to disconnect everything every night or take many risks letting it outdoors. It had multiple connection issues due to a poor quality usb hub, many serial interfaces and suffered of an obvious lack of protection.

When I returned to astrophotography last year I considered the need of making a serious project for an AstroHub device.

BRIEFING

A portable suitcase that allows me to fully manage an astrophotography session in a very short time. That means that should include all the necessary (apart of the telescopes, mount, cameras and computer) to perform an imaging session and it has to be very simple and easy to use.

LAYOUT

Imagen3.1

Note that the PC is not included in this Astrohub. That’s beacuse this computer is not only dedicated for astrophotography. Is my personal computer.

USER REQUIREMENTS

  • Connect and power all the equipment
  • Quick setup time
  • Cheap
  • Reliable
  • Portable lightweight.
  • Sturdy, dustproof and reasonably waterproof.
  • Flexible power input (AC 220V and DC 12V)
  • Monitored power
  • Ready for future upgrading

EQUIPMENT REQUIREMENTS

The devices of my equipment that must be powered/controlled are:

  • Imaging Camera: QHYCCD 163M
  • Filterwheel: QHYCCD CFW2M-US
  • Guide Camera: QHYCCD 5R-II
  • Mount: SKYWATCHER HEQ5
  • Laptop: ASUS ZENBOO UX-32VD
  • Flat Panel: DYI FLAT PANEL (Eventually)

The filterwheel is directly connected to the imaging camera, so it can be excluded from the analisys.

The following table is a summary of the requirements to control and power this astronomical equipment.

Imagen1.png

The accesories bag has to have all the essential, but only the essential, accesories needed to do a astrophotography session. The tasks involved may include to adjust knobs, focus, take flats, take notes…

ANALYSIS

  • Cable management is the slowest task to do. Focus on it.
  • Cables around the computer is annoying. Use a USB Hub.
  • I only have 1 imaging camera, 1 guide camera and 1 mount, so I always use the same cables, so cables can be wired togheter.
  • Data integrity is crucial.
  • All the devices use DC so a AC/DC power supply  is needed.
  • There are devices sensitive to voltage drops, so the power should be monitorized and controled by a Control Panel.
  • In my case, I don’t need to make flats every session, because the sensor of my camera is enough protected with the filterwheel, so the Flat panel cable should have a removable connection.
  • In the case of a multiday session, the equipment will be left outside, wired, so the case must be prepared to be left outside also.

DEVELOPMENT

As commented in the briefing, the goal is to power the equipment, to control it, to manage the cabling and to contain an additional stuff and all this has to be contained in a case, so we can divide the development in 5 parts:

  1. CABLE HUB
  2. DATA HUB (USB)
  3. POWER HUB (Power Panel)
  4. ACCESORIES
  5. CASE

Although the different aspects, there are some relationships between them to take into account. POWER HUB and DATA HUB should be near one each other in order to have a common space in wich power and data cables will join to go together to the CABLE HUB and then to the astronomical equipment. The CABLE HUB should be somenthing near to a circular area, in order to avoid the cables to be blended excessively. The ACCESORIES can be placed on top of the cable hub or inside the loop of the cabling.

The basic layout can be something like this:

Imagen2

CABLE & DATA HUB

The cables are the center of the project as they are so I decided to start the development of the project with the cable study. The Data Hub will consist in a single component, the USB Hub, so has been included in this section also.

REQUIREMENTS

  • Quick setup
  • Allow to point the telescope to any coordinates.
  • Reliability
  • Allow enough connections for future equipment

LAYOUT

The data comes from the equipment by 3 usb cables, one from the mount, one from the imaging camera, and one form the guide camera. This cables are connected to a usb hub and one usb cable goes from the usb hub to the computer.

I’ve decided to group all the cables, clamp them to the DEC Axis, let some cable lenght to allow the mount to move at any coordinate, clamp them again to the RA Axis, and then let them go to the Astrohub.

Imagen8

ANALYSIS

There are some aspects to consider about cables:

The most important issue when cabling is cable snags. There are have many cables, many knobs, and the mount has a wide movement during an astrophotography session. Once snagged the cables can be accidentally disconnected from its device, causing a loss of data or power,  or even worst, they can break the connector of the device, and do an irreversible damage to it. Astrophotography equipment is very expensive so it’s important to invest enough time to avoid this issue.

The lenght of the cable is the main aspect be considered to avoid snags. A cable too short not only will snag, it also will cause a restriction on where the telescope can point to, or where the Astrohub can be putted. Otherwise, data cables too long can suffer data losses.

To clamp the cables to fixed points (of the mount) is a good idea to protect the equipment against snags. For example, to clamp the cables from the cameras to a safe point like the telescope rings, or the DEC Axis of the mount.

How to wire the cables is very important to avoid snags. One big cable is less susceptible to snag in a knob than a lot of thinner ones.

Another point to consider is the weight of the cables. Some cables, as USB Shielded cables are quiet heavy. If we let them hanging from the camera, for example, it can cause a flexure of the optical train that will lead to a inefficient guiding. Again, to clamp the cables to the mount can release the equipment form holding the cables.

As I choosed to wire the cables together, both data and power ones, there is a electronic issue to consider, the electromagnetic interferences (EMI). This interferences can introduce noise to the images, or produce data losses, that can lead to a inconsistent guiding, corrupted images, hangs…

So we have four aspects to specify, the position of the clamps, the lenght between clamps (and the total lenght), how to wire the cables together, and how to avoid EMI.

HOW TO DETERMINE CLAMP POINTS

As a general rule, the best situation for a clamp point is as near as possible of othe geometric axis of the mount. In fact, some mounts are prepared to install the cables inside the axis, but for the rest of the mounts, one have to define this points.

The point that I have selected for the DEC Clamp is the knobs of the saddle plate. This point should be clamped as strong as possible. This will protect the equipment to suffer in an eventual snag from the cable below this point. Right now I have clamped it with elastic cord, but I will improve it with a stronger clamp.

In the case of the RA axis I used the polarscope cover as a support of this clamp. The polarscope cover of the HEQ5 is attached directly to the RA Axis so it moves in solidarity with it. That means that when campled on it, the position of the cables to the mount doesn’t have a relative movement and can be very short.

IMG_20180715_175759_LT

HOW TO DETERMINE CABLE LENGHTS

As commented before, shorten cables will cause restrictions, but long cables could cause another issues also (snagging, data transfer issues…) so to choose the correct lenght is important.

I have used a simple workflow to make this calculation.

Note: If you are attempting to determine wich cables you should buy, you can proceed with old cables, or even with cord or rope. Simply take into account the extra lenght for the USB connectors dimensions.

  • Connect all the cables to the equipment as for a usual astrophotography session.IMG_20180715_200442.jpg
  • Group the optical train cables (we will name it as DEC Cables) with removable fasteners (like velcro straps or small pieces of wiring spiral) and choose a DEC Clamp. The general rule to determine a Clamp point is to search for a point as near to the geometric axis as possible. If the cable passes through the axis it will only rotate, and his position relative to the RA Clamp will remain constant. This will allow to shorten the cable lenght. Use a removable fastener for fine tunning the lenght.IMG_20180715_200613
  • Rotate the camera to +90º and -90º. In my opinion more than that has no sense , because in that case I will choose the oposite position, but for other setups, maybe other angles should be considered.IMG_20180715_200833-lt.jpg
  • Shorten the cables as much as possible. In my case, I have to add some extra lenght for my other optical train, that is slightly longer.IMG_20180715_201006.jpg
  • Make sure that the devices can be desconnected if necessary.IMG_20180715_201054.jpg
  • Join the DEC Cables with tape in the DEC Clamp position. This will keep the relative position of each connector and will allow to remember where the cables must be attached to the DEC Axis when the cables are unclampled.IMG_20180715_201919.jpg

Now the DEC Cables lenght and the DEC Clamp can be considered fixed. We can continue with the RA Cables and RA Clamp.

  • Connect the Mount Cables.
  • Rotate the DEC axis 180º from Home Position.IMG_20180715_201216.jpg
  • Rotate the RA Axis to +120º and -120º (or more) form the home position and clamp the cables to the RA Clamp in the position where the lenght is maximum.IMG_20180715_201351.jpg
  • Double check that all the cables have the same distance between the clamp points and group the DEC Cables and the Mount Cables with tape in the RA Clamp position.  img_20180715_2019231.jpg
  • Return the mount to Home Position and check that the Mount Cable doesn’t hit the DEC Cable.img_20180715_2018062.jpg
  • Let the cables to hang to the floor and add the necessary lenght to reach the USB Hub in the expected position of the Astrohub Case. Put a mark on this point.IMG_20180715_202043.jpg
  • Now you can unclamp the cables from the equipment and measure them.

After doing this procedure, this is the result for my setup:

cable lenght.png

Note that the distance between the RA Clamp and the floor is between 1m and 1.2m. That’s because I have to manage two observatories, one with a tripod and one with a pier and they have different heights.

As a conclusion, I will need 3m cables for the cameras and 2m cables for the mount.

CABLE WIRING

There are several ways to wire the cables. Velcro straps, adhesive tape, cords… In my opinion all this method have an inconvenient: they clamp the cables in one single point, so between clamps, the cables are still free, and this increases the possibility to be snagged. My suggestion is to use spriral wraps. Polyethylene ones are my preference because they are soft and therefore esaier to blend.

products_29799_ctw25w_1.jpg

In previous versions of the astrohub, the cables become rigid once wrapped and they were difficult to blend and route.

My suggestions for a safe and easy wrapping are:

  • Don’t use spirals with diameters smaller than the diameter of the cables once grouped.
  • Avoid to wrap too tight or the cables will become rigid.
  • Respect the spiral pitch. An elongated wrapping introduces tightness too.
    29b3c58f7bc435ffdcacf647d9574be2
    Elongated wrapping
swb15-clear-spiral-wrap-2
Correct wrapping
  • Wrap the cables slightly blended. This will let them preformed as a loop and will be easier to store them in the case without causing tensions.
Z_xGL-icpEx_
  • To split the spiral wrap in many parts makes wrapping easier, but is more reliable not to split… I splitted the wrapping in 2 parts because the section from the case to the mount has to carry 5 cables, but the section from the mount to the cameras has 3 cables, so I used two different diameters of spiral wraps.

To wire 3m of a group of 5 or more cables is a little bit tricky, but the effort worth it.

IMG_20180715_175759

EMI PROTECTION

As commented, EMI (Electromagnetic Interferences) can be produced when data cables and power cables are wired together. This interferences can result in noise in the images, banding, or corrupt data. To avoid this one option is to wire data lines and power lines at a certain distance or, if they have to meet together, they should cross at 90º. A third option is to use shielded cables. As I’m planning to wire the cables together in parallel, the cables should be shielded to avoid inteferences.

61U2W4oO2nL._SL1001_3
Shielded cable scheme. Note the two external covers (shield) and that the internal power line is placed between the two shields.

SELECTED CABLES

The following table shows the selected components:

cable data table.png

MOUNT: INSTEIN EQDIR – USB2.0 / RJ45 – 2m (33€)

s-l1600.jpg

This is an improvement from the older EQDIR device, that had a serial-to-serial interface and needed an additional serial-to-usb converter. In this new cable the serial-to-usb converter in embedded in the usb housing and includes the Prolific PL2303 chip. The cable is shielded and is 2.5m long.

IMAGING CAMERA: DELOCK USB 3.0 – MALE A / MALE B – 3m (16€)

56f259910eef37-682251592

This is the cable for the imaging camera so it has to be the best possible in terms of shielding and reliability. It’s from the brand DeLock, usually used for audio edition interfaces. The connectors are gold-plated and is double shielded.

GUIDE CAMERA: UGREEN USB 2.0 – MALE A / MALE B – 3m (9€)

61FqhPygI1L._SL1001_.jpg

This is the cable for the guiding camera. Is shielded, the conductors are made of cooper and the connectors are plated (I assumed not gold plated).

HUB TO LAPTOP: UGREEN USB 3.0 – MALE A / MALE A – 2m (9€)

61yC8r-9GIL._SL1001_.jpg

This is the cable for the connection between the USB Hub and the laptop. Its lenght is 2 meters intead of 3 meters of the other cables. I prefered it to be sightly shorter because this cable has to manage all the data produced by the other 3 cables and the general rule for reliability is that the shorten cable, the more reliable is. Is commontly accepted that the maximum leght for non powered cables is 2m. As the guiding camera cable, is shielded, the conductors are made of cooper and the connectors are plated.

USB HUB: QICENT USB HUB 3.0 10 Ports (Powered) (31€)

I selected this hub because is USB 3.0, is powered, has led indicators, and 10 ports (2 of them for powering only).

Resultado de imagen de qicent 10 ports

POWER HUB

The power hub has to control and monitor the powering of different devices. It must be able to be powered by 220V AC or 12V DC, and the astronomical equipment must be protected against any electric damage.

REQUIREMENTS

  • Avoid to mix data electronics and noisy components, like motors, in the same powering lines
  • Ensure stabilized voltage fot HEQ5 (is very sensitive to voltage drops)
  • Allow voltage and amperes monitoring
  • Avoid voltage drops
  • Avoid overload
  • Allow different load inputs (12V DC and 220V AC)
  • Keep power supply at low temperature
  • Allow enough power for future equipment
  • Allow enough connections for future equipment

LAYOUT

One AC cable gives power to 3 DC12V Power Supplies. Each of them goes to a switch, a DC IN/OUT, a fuse, a voltimeter-amperimeter monitor, a DC hub and finally every component of the equipment is wired with his own cable. My mount is sentitive to voltage drops so I included an additional voltage stabilizer rated at 13V.

POWER HUB LAYOUT.png
POWER HUB WIRING.png
Wiring Diagram

ANALISYS

The most importat calculation to be done is the load analisys to determine the requirements for the PSUs. This analysis has to take into account not only normal operations but high demand situations also.

Other aspect to be considered is voltage drops as some devices are very sensitive to them and can cause malfuctions.

LOADS

In order to know how much power we need on every line, we must check the max power needed for every components. It’s important to stress every device in order to check the maximum comsumption. The 163M has a TEC cooling, so I measured it trying to reach a temperature impossible to reach, to force it to cool at 100% of power. The mount was measured when slewing both axis at maximum rate. The USB Hub was tested setting both cameras at maximum fps, while mount was slewing, and a flat panel and a USB led lamp was connected to the charging ports.

Imagen4
Note that the USB Hub 3.0 is rated to 4A max. The maximum power need that I’ve tested is doing panetary imaging when the 163M is downloading at max data rate. At this case the hub consumes 1.5A. I think that 4A should be when two gadgets using the power USB Ports are charging at full rate. I assumed then 1.5A as this is not the intended use.

VOLTAGE DROPS

First prototypes of this astrohub had voltage drop problems. One of the causes that I considered was if cable sections were too small. After an analisys, the conclusion was that they were OK (oversized, in fact) so I keep them. The following calculations can used to determine the optimum cable section.

The voltage drop formula is:

Vd = I · Rc

where:

Vd: Voltage Drop (V)

I: Max. Intesity (A)

Rc: Resistance of the wire (Ω)

… and the resistance of the wire should be calculated by:

Rc = ρ · (L/S)

where:

ρ: Wire Resistivity (Ω·mm2/m)

L: Cable Lenght (m)

S: Cable Section (mm2)

Combining both formulas:

Vd = (I · ρ · L) / S

This formula can be expressed as:

S = (I · ρ · L) / Vd

I will assume that a voltage drop of 0.1V is admisible.

The material of the wires is cooper and its resistivity is 0.0172 Ω·mm2/m.

With this data we can calculate the optimum section for each cable. In my case I have to calculate 3 cables (Mount, Camera and PC):

Mount Cable (L=1m / I=1.5A)

Min. Section = (1.5 · 0.0172 · 2) / 0.1 = 0.5 mm2

Camera Cable (L=3m / I=2A)

Min. Section = (2 · 0.0172 · 6) / 0.1 = 2 mm2

PC Cable (L=2m / I=3A)

Min. Section = (3 · 0.0172 · 4) / 0.1 = 2 mm2

SELECTED COMPONENTS

As one of the main constrains given by the briefing is to be a cheap project, I have considered all my old electronic stuff and buyed generic components.

power hub table
Note: To calculate the real cost (no reclycled stuff) add about 40€, so Total Cost : 100€ aprox.

DATA POWER SUPPLY: QHY163M POWER SUPPLY – 12V 6A (0€)

I have a 12V-6A power supply that I received with my camera and it has been assigned to the data electronics line, where the camera is included, to assure that the camera receives the current from the power supply that has been tested to work with.

MOTORS POWER SUPPLY: GENERIC – 12V / 4A (0€)

A power supply from some old stuff, but seems to work well.

LAPTOP POWER SUPPLY: TACENS ORIS DUAL II 100W – 12V / 5A (28€)

To power a laptop is not as easy as the other components because most of them work at different voltage than 12V. Mine is rated at 19V, and thats a problem in terms of power flexibility. If I bought an standard AC/DC computer power supply, I will not be able to power the laptop with a battery unless I include a step-up device. I tried with one of them and the result was not good, it had poor efficiency, reached too high temperatures, sometimes stopped working… not the reliability that I’m searching for.

Looking to other devices I found this:

Resultado de imagen de tacens oris dual ii 100

It’s realibility is very good so no power failures. The frame is from aluminium and the heat dissipates correctly and is always cool. It has a wide range of voltage outputs (12 – 24V) so can be used with future laptops if necessary. It’s cheap, about 28€, and the most important, can be powered with either 12 DC or 220V AC.

DC/DC STEP UP-DOWN

This device can magane an input from 1.25V to 26V DC and gives a constant output voltage (adjustable) with a maximum load of 3A. I will use it to keep the voltage of the mount at 13V. I noticed that this device gets hot during long sessions and suffers some voltage drops, not dangerous, about 0.1-0.2V, but anyway I’ve considered that it has to be cooled.

step-up-dowm.jpg

DIGITAL VOLTIMETER-AMPERIMETER

This monitor are not really mandatory and in fact they have their own consumption (not sure how many, but I think about 0.3A), but I want to have a exact control of the comsumption of the different circuit to calculate exactly wich batteries capacity I will need for outdoor astrophotography.

volt.jpg

SWITCH, DC IN, FUSE…

This are generic and inexpensive components. In my case they have to be wall mounted type.

ACCESORIES

As commented, the AstroHub has to be able to manage an entire astrophotography session. The problem of this statment is that many times is understtod as «carry all you can». I used to carry too many things «just in case» and this casuses to have oversized cases with many things that are never used. In this case I betrayed myself and forced me to think in wich accesories are really mandatory for my setup.

REQUIREMENTS

To identify the accesories that I will need, one has to built a list. Note that some usual tasks are not included. That can be, or because I optimized them in other projects (I don’t need to balance my setups, for example) or because is not a need for me at this moment (I haven’t imaging outdoors with my new equipment yet).

LAYOUT

The accesories have to be accesible and well arranged into a softcase.

ANALYSIS

To identify the accesories that are really mandatory I started by including nothing and do many imaging sessions. Every accesory needed in a standard session was included on the list.

It’s very important to exclude those accesories used in sessions with major issues. For me it makes no sense to include, for example, a toolbox with all the necessary to disassemble the mount. If something serious happens to the mount in an imaging session, I will choose to abort the session immediately. To try to fix major disasters in the middle of an astrophotography session hoping to finish on time to start imaging has been one of my biggest mistakes during many years.

SELECTED ACCESORIES

So, once this process was finished I considered that the essential accesories for my setup are:

  • 3 Bathinov Masks
  • MicroUSB Cable
  • Flat Panel
  • Notebook+Pen
  • USB LED Lamp
  • Headlamp
  • Basic Mechanical Tools (Screwdriver, Allen, Plier…)
  • Backup Cables

Although this list is considered as essential actually the only accesory that I use every session is the bathinov mask.

As this accesories have been reused from old stuff, I haven’t made a cost analysis. Simply take into account that the flat panel was 18€ and the led lamp can be ordered for 4-5€.

Note that I don’t include in this list gloves, huts, or any clothe.

CASE

The functionality of the case is not only to contain all the stuff. As commented before it has to be easy to use and able to withstand outdoor use.

The case has to be the last component of this Astrohub to be developed. It makes no sense to buy it before as it can become too small to include all the accesories or too big and the components can suffer during transportation.

REQUIREMENTS

  • Cheap
  • Reliable
  • Portable lightweight.
  • Sturdy, dustproof and reasonably waterproof.

LAYOUT

The cables will go outside the case from the front side, avoiding to disturb other components. The power hub and the data cable, as commented at the start of the development, should be placed one near the other to reduce cable lenghts to the minimum. The accesories can be placed above the cable hub. The flat panel will be placed attached to the lid to not to cover the rest of the components.

ANALISYS

One of the things that I realized when constructing first prototipes is that is so difficult to attach the components in a single layer box. It is not possible to drill the case without loosing its waterproof characteristics, in addition, the screws will go outside making transportation and storage uncomfortable. That’s why I consider that a double layered case is an important requirement.

Another requirement that I considered is to have a lid with limited opening. This allows the lid to stay at vertical position, making the management of the accesories easier. In addition, the case uses less space when deployed.

About the opening, can be useful to choose a case that doesn’t open just by the middle of the case. That will allow to have a base with bigger depht to store big devices (like the PSU) or assemblies (USB Hub with some devices connected), and a lid to store flat devices (Flat panel, Bathinov masks, filters…)

Pelican Cases are widely used for photography equipment storage so they are a good option to consider. They are made of plastic so they are lightweight and are reasonably waterproof too. The counterpart is that they are usually expensive.

SELECTED CASE

I selected a hardcase from Keter that is sturdy, waterproof (not certified), big enough and cheap (28€). The external dimensions are 470x380x175mm.

Resultado de imagen de KETTER HARD CASE

It was designed for tools storage so it has a big main container with dividers and a thinner lid that includes a panel to hold tools (easily dettachable).

Resultado de imagen de KETTER HARD CASE

The internal dimensions of the main container are 400 x 300 x 130 mm. The container is also detachable in two pieces. This will allow to work (drill, cut…) the internal container (red) without damaging the external container.

Resultado de imagen de KETTER HARD CASE

CONSTRUCTION

PREPARING THE LAYOUT

First I decided how to divide the space in the internal cavity, I took profit from the dividers to follow the basic layout described in the development section:

BASIC LAYOUT.png

BUILDING THE POWER HUB

This is the layout explained before:

POWER HUB LAYOUT.png

…and this is the execution:

img_20180721_161647-e1532389610914.jpg

First I cutted a thick cardboard from an old school folder and I used it as a panel and attached the PSUs with plastic clamps. On the preliminary tests the Tacens PSU remain fresh, but the other 2 PSUs become a little hot. I decided to drill their frames to increase air flow and therefore, heat disipation.

IMG_20180721_161815

I soldered cables directly to the AC input of the PCB’s  to avoid issues with the connectors.  In addition it allow me to avoid the usual big AC connectors (not the Tacens, too new to take risks). The 3 inputs are connecter together to a standard AC Plug.

IMG_20180721_161810_HHT.jpg

Each output of the PSU are wired with long enough cable to reach the sequence switch, DC IN, fuse, and finally the digital voltimeter.

img_20180715_0029471.jpg

From each voltimeter comes out one cable that power one DC Hub module.

To build the DC Hub I assembled 6 Wago connectors with heat silicon. From the DC Hub come out the different wires to the devices. The one for the mount has to go first to the voltage stabilizer. The fan is in fact a motor, so is connected to the Motors circuit

IMG_20180721_161827_HHT

Once done, the cardboard has been screwed to the inner container. The cable output has been done to go to the Data Hub to join with the corresponding data cable.

IMG_20180721_161847_HHT.jpg

BUILDING THE DATA HUB

The Data Hub is very simple, so no layout is needed.

The USB Hub has been oriented upwards for easy connection and clamped to the inner container with plastic clamps.

img_20180715_181926.jpg

BUILDING THE CABLE HUB

This is the layout:

cable lenght

To build the cable hub the only task is to use a spiral wrap and wrap the cables. I started wrapping from the DEC Clamp to the RA Clamp, letting enough spiral on the sides to reach the cameras and the USB hub. (Sorry, no photos here) From there then I finished to wrap the cables to the end.

This is the result:

dav

Something that has always worried me is what to do with cables when I pretend to imaging during several nights. I used to let the lid partially opened, to not to damage cables, but it is very risky if it rains. I couldn’t fix it completely but I tried. I drilled a hole to the external case, but only cutted a bit the inner container and make «door» to let the case «reasonably» waterproof.

img_20180721_175514.jpg

With this modification I can let the astrohub outdoors, even without cover it.

dav

FINAL RESULT

And its done, thanks for watching, and any suggestion is welcome!

IMG_20180721_172704
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